1. Field of the Invention
The present invention generally relates to an electronic engine control system and more particularly, to an improved system and method for determining whether or not combustion of an air-fuel mixture takes place during engine operation.
2. Description of the Related Art
A conventional electronic engine control system typically comprises an electronic control unit and a variety of sensors. These sensors include, among others, an airflow sensor to measure the amount of intake air, and a cylinder head coolant temperature sensor to detect an engine temperature. The electronic control unit is a preprogrammed computer operable to receive from the sensors information on various conditions of the engine such as engine temperature and engine speed. The microprocessor then analyzes this information and signals injection valves to deliver a proper amount of air-fuel mixture.
Japanese Patent Public Disclosure (Kokai) No. 61-201135 (1986) discloses an improved electronic engine control system operable to detect whether or not spark plugs are properly operated during engine operation. The disclosed prior art system includes a plurality of exhaust gas temperature sensors mounted to an exhaust manifold to detect the temperature of exhaust gases from engine cylinders, and a potentiometer for providing a reference temperature range. The reference temperature range is an exhaust gas temperature range when the spark plugs are properly operated to combust an air-fuel mixture in the engine cylinders. A central processing unit is provided to analyze the input information from the exhaust gas temperature sensors and then calculate the average exhaust gas temperature. The difference between the average gas temperature and each actual exhaust gas temperature is compared with the reference temperature range to determine whether or not each spark plug is properly operated to combust the mixture. However, the prior art system is not always reliable in that the exhaust gas temperature may increase with engine load and the speed of rotation of the engine.